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Title: Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer

Abstract

Purpose: The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H and N) cancers. Methods: The authors employed two types of mock phantoms: large-sized head and neck (LH and N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S and S-IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH and N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S and S-IMRT. For VMAT, single arc (VMAT{sub 1}) and double arc (VMAT{sub 2}) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the numbermore » of segments for each plan. Results: 2.5-mm MLC showed better dosimetric characteristics in S and S-IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p < 0.05). However, no significant dosimetric benefits were provided by the 2.5-mm MLC for LH and N (p > 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH and N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH and N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was greater than 95% according to the 3%/3 mm criteria. There were no significant differences in dosimetric error between the 2.5- and 5-mm MLCs. Conclusions: As compared with MLC of 5-mm leaf widths, MLC with finer leaf width (2.5-mm) can provide better dosimetric outcomes in IMRT for C-shape. However, the MLC leaf width may only have minor effects on dosimetric characteristics in IMRT for LH and N. The results of the present study will serve as a useful assessment standard when assigning or introducing equipment for the treatment of H and N cancers.« less

Authors:
; ; ; ; ; ;  [1]; ;  [2];  [3]
  1. Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710 (Korea, Republic of)
  2. Department of Radiation Oncology, Kangbuk Samsung Hospital, Sungkyunkwhan University School of Medicine, Seoul 110-746 (Korea, Republic of)
  3. Department of Biomedical Engineering and Research Institute of Biomedical Engineering, The Catholic University of Korea, Seoul 137-701 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22251681
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 41; Journal Issue: 2; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; COLLIMATORS; COMPARATIVE EVALUATIONS; ERRORS; HEAD; NECK; NEOPLASMS; PHANTOMS; RADIATION DOSES; RADIOTHERAPY; SPINAL CORD; VERIFICATION

Citation Formats

Hong, Chae-Seon, Ju, Sang Gyu, E-mail: sg.ju@samsung.com, Kim, Minkyu, Kim, Jin Man, Han, Youngyih, Ahn, Yong Chan, Choi, Doo Ho, Park, Hee Chul, Kim, Jung-in, Nam, Heerim, and Suh, Tae-Suk. Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer. United States: N. p., 2014. Web. doi:10.1118/1.4860155.
Hong, Chae-Seon, Ju, Sang Gyu, E-mail: sg.ju@samsung.com, Kim, Minkyu, Kim, Jin Man, Han, Youngyih, Ahn, Yong Chan, Choi, Doo Ho, Park, Hee Chul, Kim, Jung-in, Nam, Heerim, & Suh, Tae-Suk. Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer. United States. https://doi.org/10.1118/1.4860155
Hong, Chae-Seon, Ju, Sang Gyu, E-mail: sg.ju@samsung.com, Kim, Minkyu, Kim, Jin Man, Han, Youngyih, Ahn, Yong Chan, Choi, Doo Ho, Park, Hee Chul, Kim, Jung-in, Nam, Heerim, and Suh, Tae-Suk. 2014. "Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer". United States. https://doi.org/10.1118/1.4860155.
@article{osti_22251681,
title = {Dosimetric effects of multileaf collimator leaf width on intensity-modulated radiotherapy for head and neck cancer},
author = {Hong, Chae-Seon and Ju, Sang Gyu, E-mail: sg.ju@samsung.com and Kim, Minkyu and Kim, Jin Man and Han, Youngyih and Ahn, Yong Chan and Choi, Doo Ho and Park, Hee Chul and Kim, Jung-in and Nam, Heerim and Suh, Tae-Suk},
abstractNote = {Purpose: The authors evaluated the effects of multileaf collimator (MLC) leaf width (2.5 vs. 5 mm) on dosimetric parameters and delivery efficiencies of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for head and neck (H and N) cancers. Methods: The authors employed two types of mock phantoms: large-sized head and neck (LH and N) and small-sized C-shape (C-shape) phantoms. Step-and-shoot IMRT (S and S-IMRT) and VMAT treatment plans were designed with 2.5- and 5.0-mm MLC for both C-shape and LH and N phantoms. Their dosimetric characteristics were compared in terms of the conformity index (CI) and homogeneity index (HI) for the planning target volume (PTV), the dose to organs at risk (OARs), and the dose-spillage volume. To analyze the effects of the field and arc numbers, 9-field IMRT (9F-IMRT) and 13-field IMRT (13F-IMRT) plans were established for S and S-IMRT. For VMAT, single arc (VMAT{sub 1}) and double arc (VMAT{sub 2}) plans were established. For all plans, dosimetric verification was performed using the phantom to examine the relationship between dosimetric errors and the two leaf widths. Delivery efficiency of the two MLCs was compared in terms of beam delivery times, monitor units (MUs) per fraction, and the number of segments for each plan. Results: 2.5-mm MLC showed better dosimetric characteristics in S and S-IMRT and VMAT for C-shape, providing better CI for PTV and lower spinal cord dose and high and intermediate dose-spillage volume as compared with the 5-mm MLC (p < 0.05). However, no significant dosimetric benefits were provided by the 2.5-mm MLC for LH and N (p > 0.05). Further, beam delivery efficiency was not observed to be significantly associated with leaf width for either C-shape or LH and N. However, MUs per fraction were significantly reduced for the 2.5-mm MLC for the LH and N. In dosimetric error analysis, absolute dose evaluations had errors of less than 3%, while the Gamma passing rate was greater than 95% according to the 3%/3 mm criteria. There were no significant differences in dosimetric error between the 2.5- and 5-mm MLCs. Conclusions: As compared with MLC of 5-mm leaf widths, MLC with finer leaf width (2.5-mm) can provide better dosimetric outcomes in IMRT for C-shape. However, the MLC leaf width may only have minor effects on dosimetric characteristics in IMRT for LH and N. The results of the present study will serve as a useful assessment standard when assigning or introducing equipment for the treatment of H and N cancers.},
doi = {10.1118/1.4860155},
url = {https://www.osti.gov/biblio/22251681}, journal = {Medical Physics},
issn = {0094-2405},
number = 2,
volume = 41,
place = {United States},
year = {Sat Feb 15 00:00:00 EST 2014},
month = {Sat Feb 15 00:00:00 EST 2014}
}